Photoacoustic tomography (hereinafter referred to as PAT) is attracting an attention as a method for specifically imaging new blood vessels due to cancer. The PAT is a technology of an imaging system involving irradiating an analyte with illumination light (near-infrared light) and receiving photoacoustic waves generated from the interior of the analyte with an ultrasonic probe. The details of this photoacoustic apparatus are described in NPL 1. However, NPL 1 does not give sufficient consideration to illumination-light irradiation control, in particular, safe irradiation. This sometimes causes the illumination light to irradiate not only the interior of the analyte but also space, and hence there is much room for further improvement in the safety of illumination light irradiation.
On the other hand, a known technology for the safety of irradiation of illumination light, such as laser hair removal, although not the PAT technology, is disclosed in PTL 1. FIGS. 8A and 8B illustrate the configuration of PTL 1. In FIGS. 8A and 8B, an energy releasing surface 101 is a surface that comes into contact with skin, which is to be irradiated with energy, such as light. A support structure 102 holds the energy releasing surface 101 and is accommodated in a housing 104, with contact sensors 103 disposed therebetween. The contact sensors 103 detect contact between the energy releasing surface 101 and skin (not shown) and are disposed so as to surround the energy releasing surface 101. Release of energy is stopped until contact with skin is detected by the contact sensors 103. This allows energy to be emitted only when the energy releasing surface 101 is in fully close contact with skin, thus improving safety in energy irradiation.
However, the related art has the problems below.
In the case of irradiation control using the contact sensors 103, since emission of energy, such as light, is determined depending on whether or not there is contact, the emission has to be stopped depending the object in contact. For example, because energy, such as light, is emitted even if an object other than an object to be irradiated with light is in contact, further improvement has been required. Also when a transparent substance is in contact with energy, such as light, the energy that has passed through the contact object irradiates another object, and thus improvement is needed. Accordingly, control of energy release using the contact sensors 103 is not necessarily perfect, and thus a different safe measure is needed to further improve the safety.